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ProjectWolfDragon LiPO PCB LITE voltage Monitor

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Many of you have had a chance to read my Lithium Polymer Battery Primer, and have made the exciting dive into the world of lipo batteries. I'm excited to see that there is a movement among manufacturers to embrace these somewhat new battery chemistries and dispel the "black magic-voodoo" mentality that surrounds them. With the ushering in of users new to the world of lipoly batteries, comes the fear of destroying a new battery, and possibly a gun due to running the voltage low on your pack. Since lipoly batteries have a lower limit of 2.8v (with 3.0v being the lowest you really ever want to go), you do need to be cautious not to waste your brand new battery pack. Several people have gone to Ebay and such places in search of products to keep their lipo in the safe operating range (3.0-4.2v per cell). Most of these products were never intended for Airsoft use, and as such fail. Most of them can't cope with the sudden drops in voltage and cause false alarms. Others are just made of poor materials and workmanship. To the rescue comes Wolfdragon and his "Over-Discharge Protection Circuit Boards for Lithium Polymer (LiPO) Battery Packs". These come in two varieties, and today we'll be testing out the "Lite PCB". The largest difference between the "Lite" model and the regular is the ability to cut power from the battery in a low voltage state (i.e. the battery is at the 3.0v lower limit). While the "Lite" model does not cut off power from your battery to the gun, it will notify you via LED or buzzer when you reach that lower limit, but the user must then disconnect the battery himself/herself.


First Impression

I am very impressed with the kit. Unfortunately I was so excited I didn't take a picture of how everything comes in the mail. Included with the kit is the PCB itself, the buzzer, heat shrink, label (complete with serial number and version number), instructions, and appropriate balance connectors and enough wire to place it at either end of your gun. Overall I must say it is a very complete kit. The instructions seem pretty easy to follow and are well laid out. .


Materials and Construction

The balance connectors are excellent quality, and the leads are well soldered onto them. I was pleased to see the length of wire supplied makes it easy to position the unit where ever you might need it to be. The PCB is well laid out and every solder joint is well done with no excessive or stray solder anywhere to be found. The board itself is only about 1" long and about .75" wide.



The main feature (and reason for buying one of these) is the ability to notify the player when their battery is reaching that lower voltage limit, and give them enough time to swap batteries before any damage to the battery can occur. In addition to that, the "Lite PCB" also features auto battery voltage configuration. Basically it senses how many cells are in your pack (2 for a 7.4v pack, or 3 for an 11.1v pack, etc.) and configures the system automatically. That's a nice touch and makes it easier for the end user. The unit also works with battery packs from 7.4v up to 14.8v (2s-4s)



The configuration I'm using came with 1 balance tap for a 7.4v lipo, and a buzzer. Per my request, Wolfdragon also sent me a 11.1v balance tap so I can test it with both voltage batteries. First test was run with a 7.4v battery. The battery that is being used is a Thunderpower RC Pro Power 30C 2200mAh 2S (7.4v) pack. The pack came with ThunderPower balance taps, so I had to use a converter to make it work with Align style taps. No big deal as I already had one for my balancer. Plugging in the battery the LED on the PCB lights up once to let me know it's working, sends a beep through the buzzer, and then flashes the LED 2 times to let me know it recognizes the 7.4v pack. Everything is going well. The gun being used for testing is a Dboys SCAR-L running 400 FPS and putting out about 20 RPS on this 7.4v battery. Running all day long with the 7.4v battery I never had one hiccup. The PCB never gave me a false alarm. Most of the cheapo ones on Ebay often give false beeps under this load due to voltage dips while firing (more on this later). unfortunately, this great lipo lasted me all day and didn't need to be charged, and as such never tested the Lipo Lite PCB's capabilities. Excited to test this product out I tried out the 11.1v lipo on my Cyma M14 DMR running ~510 FPS in a semi only configuration. Again, it recognized the battery (this time with 3 flashes of the LED), and never once gave me a false beep. Being that I did not charge this battery before the skirmish, I was fairly certain that I'd either trash the battery or hear the heavenly beeping sound of the Lipo Lite PCB telling me the battery is low. Several games into the day I take down several opposing players in quick succession. Then it happened. A faint beeping noise. It took me a minute to figure out what was beeping, but I soon realized it was the Lipo Lite PCB. I had positioned the speaker in the back of the stock where it would be close to my head and I would be sure to hear it. Some people don't like the idea of a beeper thinking it would give away your position (you can get this with an LED only), but the sound was quiet enough that it's not obvious more than a few feet away, yet loud enough for the user to notice. I think it's perfect in volume, and figure, changing the battery in my gun is a noiser operation than the beeper going off. Later I had a chance to examine the battery. unfortunately I did not get around to doing it the day of the game, but rather the next morning. What I found was that the three cells registered: 3.7v, 3.4v, 3.7v. Now the true lower limit of a lipoly battery cell is 2.8v. At that point the cell is nothing more than a paperweight. The alarm in the PCB Lite, alerts the user once a cell drops to 3.0v. Now you're wondering... why did the alarm go off if the battery pack's lowest cell was 3.4v? Remember, I said I checked the battery the next morning. Under load the battery discharges. Once the battery has a chance to sit the voltage recovers a bit. Being that I checked the battery's voltages the next morning, the pack had a chance to recover. Most likely the pack became unbalanced under use (it is a fairly low-end pack), and the one cell dropped down to 3.0v triggering the alarm. The Lipoly PCB Lite performed flawlessly. I ran my findings by the mastermind behind ProjectWolfDragon.Com. He had this to say about my findings in regards to cheaper lower quality alternative alarm systems: "The PCB CPU constantly polls the voltage off of each cell of the battery. By comparing these voltage together, simple math can determine the voltage of each cell (C1 = Cell 1 Volts, C2-C1 = Cell 2 Volts, and C3-C2 = Cell 3 Volts). The resultant cell values are averaged over a progressive time range that itself is voltage dependent, this filters out unwanted spikes caused by normal firing cycles and thus determines the steady state voltage of the cell in what is actually a real-time dynamically varying system. This is why my PCB won't alarm until there is actually a problem, while the RC aircraft monitors will alarm with nearly every long trigger pull. The reason for this is duty cycle and resultant cell droop. An AEG is only operated on anywhere from 0-40% duty cycle in a 10 minute time period, with most AEG's (even those with hopper style magazines) being VERY hard pressed to sustain 4 minutes of constant fire before reloading. While most AEG's in a firefight do tend to fire repeatedly, it is the continuous draw that wreaks the most havoc as it causes the most severe voltage droops. Once the cell catches up to the demand, the voltage will come back up even while still under load, this return voltage is part of the key to how my PCB works as it is indicative of true cell health. Since my PCB ignores the initial firing induced droop, which is what causes the RC monitors to trip, the PCB doesn't alarm until the pack is actually in trouble. Back to duty cycle, an RC helicopter uses 100% throttle while in flight, this is 100% duty cycle, where all voltages matter, none can be ignored. Since it is 100% duty cycle, there are no induced droops, the pack simply starts at full power and steadily drifts downward toward full discharge. Thus the completely different way of handling dead pack detection. That's the short version of how the little suckers work and why RC monitors lie."



When it comes down to it, Lipos are the best bang for the buck battery out there. At the same time, they do require a bit more care than your regular NiMH or NiCad batteries. Filling the void with a quality product is the Lipo PCB Lite from ProjectWolfDragon.Com. Their product works flawlessly, is simple to install, and couldn't be any easier to use. It's an investment that will prolong the life of your battery and save some of that change in your pocket!


The Numbers:

Price: $17.50 as tested

Construction: 5/5 The construction was spot on with no excessive solder and everything needed to install included.

Features: 5/5 It protects your lipo from dying from over discharging, and offers auto configuration for any 2-4 cell battery pack.

Performance: 5/5 It does one thing, protect your lipo, and it does it well without flaws.




Infected Airsoft

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